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More robust handling of type variables in mcomp #1517

merged 3 commits into from Dec 7, 2017


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trefis commented Dec 6, 2017

When comparing two types, Ctype.mcomp asserts that if neither of them is a variable, then they can't both be expanded to a variable.
The first commit adds an example of a code to the testsuite showing that this assertion doesn't hold.

The second commit removes the assertion and handles variables in the exact same way as before expansion of the types.
MPR#6158 and the related commit seem to confirm that this is the correct fix.

The handling of variables pre-expansion is redundant, but I left it in place to serve as a short-circuit since expansion might be costly.
I however doubt that it will be triggered often in practice, as "external" calls to mcomp are always preceeded by calls to reify.

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garrigue left a comment

Well spotted.
The fix is trivial, so please go forward and merge it.

trefis added some commits Dec 6, 2017

testsuite: add a test trigger an assert false in Ctype.mcomp.
Fatal error: exception File "typing/", line 2028, characters 30-36: Assertion failed'

@trefis trefis force-pushed the trefis:mcomp-vars branch from e7d32e7 to 0f341e8 Dec 7, 2017

@trefis trefis merged commit 148e6a2 into ocaml:trunk Dec 7, 2017

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